Open-label, single arm trial to assess the in-vivo recovery and half- life of C1-inhibitor (Human) vapor heated, IMMUNO II in asymptomatic patients with hereditary angioneurotic edema (HAE). HAE is an autosomal- dominant disorder associated with serum deficiency of functional C1- inhibitor, the primary inhibitor for C1 esterase of the complement cascade and its subcomponents C1r, C1s, and the coagulation factors XIIa and XIa. It is also an important inhibitor for kallikrein and tissue plasminogen activator. Clinical symptoms of HAE include episodic swelling of the extremities, face and bowel wall. Involvement of the upper airway, with resultant asphyxia, is a major cause of death among HAE patients. Androgens and antifibrinolytics are used to inhibit the occurrence of HAE attacks; however, though usually effective in prophylaxis, these agents are unable to prevent the progression of an acute HAE attack. At present, there is no available treatment for acute attacks of HAE in the United States. Noncontrolled studies in Europe have shown C1I-IMMUNO to be effective in the treatment of acute attacks of angioedema in patients with HAE, to remain functionally active in vivo for about 2 days, and to raise in vivo C4 levels with a lag of several hours between infusion and the increased C4 levels. Over the past 5 years at the GCRC, patients with attacks of angioedema have been treated with a concentrate of pure C1 inhibitor that has been effective and with no adverse reactions.